Mark Hogan at the Stanford Linear Accelerator Center in California, US, is developing an alternative. Together with colleagues at SLAC and at the University of California in Los Angeles, US, Hogan has created a much more compact plasma-powered accelerator.

"Taking the beam from a standard accelerator, we've been able to double the energy [from 42 gigaelectronvolts to 84 GeV]," Hogan says.

"This is an incredible breakthrough," says Harry Weertz of the Argonne National Laboratory in Illinois, US. "Now they have to work on the details," he adds, so that plasma accelerators could be used for real experiments.

Weerts also points out that it has not been possible to pass electrons through a string of plasma accelerators, to repeatedly boost their speed. As it stands, a huge boost from plasma is a one-shot deal.

Another downside, as in all these plasma accelerators, is that the incoming electron beam loses a lot of intensity. In this case, only about 1% of the electrons in the beam made it up to the highest energy.